Remove usage of DomDistillerService in ReadingListDownloadService.

ios/chrome/browser/ui/reader_mode/reader_mode_controller.mm

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #import "ios/chrome/browser/ui/reader_mode/reader_mode_controller.h"
 
 #include <memory>
 #include <utility>
 
 #include "base/ios/weak_nsobject.h"
@@ skipping 155 matching lines @@
       ios::ChromeBrowserState::FromBrowserState(_webState->GetBrowserState());
   return base::MakeUnique<dom_distiller::DistillerViewer>(
       dom_distiller::DomDistillerServiceFactory::GetForBrowserState(
           browserState),
       browserState->GetPrefs(), pageURL,
       base::BindBlock(^(
           const GURL& pageURL, const std::string& html,
           const std::vector<dom_distiller::DistillerViewer::ImageInfo>& images,
           const std::string& title) {
         [weakSelf distillationFinished:html forURL:pageURL];
-      }),
-      nullptr);
+      }));
 }
 
 - (void)distillationFinished:(const std::string&)html forURL:(const GURL&)url {
   UIView* superview = [self.delegate superviewForReaderModePanel];
   DCHECK(_viewer || [superview viewWithTag:kReaderModeViewTag]);
   if ([superview viewWithTag:kReaderModeViewTag]) {
     [self.delegate loadReaderModeHTML:base::SysUTF8ToNSString(html) forURL:url];
   } else if (_viewer) {
     [self showInfoBar:html forURL:url];
   }
@@ skipping 113 matching lines @@
 #pragma mark - InfoBarManagerObserverBridgeProtocol.
 
 - (void)infoBarRemoved:(infobars::InfoBar*)infobar {
   if (infobar == infobar_) {
     _viewer.reset();
     infobar_ = nullptr;
   }
 }
 
 @end